Steam Trap Condensate Load and Required Capacity
Running condensate load, and the trap capacity it needs at the operating differential.
Example
You enter
- Heat duty served (Btu/hr) 400000
- Latent heat hfg at pressure (Btu/lb) 945
- Safety factor (2 typical, 3 warm-up) 2
You get
- Running condensate load 423 lb/hr
- Required trap capacity 847
Checked against published worked examples from: Armstrong International.
Details, formula, and sources
ScopeThe running condensate load (heat duty / latent heat) and the required trap capacity (load x a 2x-3x safety factor) at the operating differential - undersize it and the equipment floods on warm-up. The trap is selected from the manufacturer's capacity chart at the actual differential; warm-up, modulating, and stall conditions can demand a larger factor or a different trap type. Not the IMC 307 cooling-coil condensate drain.
Formula or tablecondensate_lbhr = heat_duty_btuhr / hfg_btulb; req_capacity_lbhr = condensate_lbhr x safety_factor (2x typical, 3x warm-up / modulating).
Source and editionFirst-principles condensate-load relation and the safety-factor practice, by name; the latent heat is from the ASME steam tables. Not edition-bound.
Free accessThe condensate load is the heat duty divided by the published latent heat at the operating pressure; the safety factor is standard practice.
What governsEstimate. AHJ and licensed professional govern.
API field namesheat_duty_btuhr, hfg_btulb, safety_factor, condensate_lbhr, req_capacity_lbhr
- Latent heat hfg from the saturated-steam table at the operating pressure, entered, or computed from an entered gauge pressure by IAPWS-IF97 on a 14.696 psia atmosphereASME steam tables
- Safety factor 2x typical, 3x on warm-up / modulating service; higher factors for stall conditionssteam-trap selection practice
- Selection the trap is sized from the manufacturer's capacity chart at the actual differential pressuremanufacturer capacity chart